1. Field of the Invention
The present invention relates to a wireless communication apparatus, a wireless communication system adopting the same and a communication method thereof, and more particularly, to a wireless communication apparatus for variably allocating the transmission rate to slave devices according to service features of the slave devices, a wireless communication system adopting the same and a communication method thereof. The present application is based on Korean Patent Application No. 2001-580, which is incorporated herein by reference.
2. Description of the Related Art
Bluetooth is a communication technology that allows transmission of information such as audio or video data with the velocity of up to 1 Mbps at a distance of 10 to 100 m.
A Bluetooth apparatus performs a mutual communication according to a Bluetooth communication, and constructs a link state in which communication is enabled through operations such as inquiry, inquiry scan, page, page scan, etc. During these processes, it is determined which device is a master device and which devices are slave devices. At least one slave device is linked to one master device to form a network called a Piconet.
The master and slave devices perform a bi-directional communication via TDD (Time Division Duplex).
According to a current Bluetooth communication, one master device in the Piconet can link seven slave devices in the active state to perform mutual communication.
The master device polls the slave device in an even-numbered slot, while the slave devices polled by the master device transmit data to the master in an odd-numbered slot. If the slaves are not polled by the master device, the slaves cannot transmit data.
In the current Bluetooth communication, a round robin polling method is mainly used, which allows equal data transmission opportunity to each of the slave devices.
The master device sends a packet to the slave device in an even-numbered slot (0, 2, 4, . . ) for polling. Here, the polling packet occupies one (1), three (3) or five (5) of the even-numbered slots (0, 2, 4,. . . ). The polling packet is transmitted to allow data communication according to the order set for the slaves that maintain the link to the master device.
The slave devices polled by the master device send a packet to the master device in an odd-numbered slot (1, 3, 5, . . . ). The packets occupy one (1), three (3) or five (5) of the odd-numbered slots.
Since the current Bluetooth communication uses the round robin polling method, the master device respectively polls all the slaves in the Piconet one by one.
FIG. 1 shows timings of operations of master and slave devices in a general Bluetooth communication system.
As shown in FIG. 1, the master device first polls a slave device 1 in an M1 transmission slot. The slave device 1 in an active mode confirms that the data transmitted from the master device is addressed to the slave device 1, and transmits the data to the master device in an S1 transmission slot that is assigned after a master transmission section.
Likewise, the master device sequentially polls the slave devices 2 and at a certain slot interval.
Then, the slave devices 2 and 3 sequentially transmit data to the master device at a certain slot interval according to the order of polling of the master device in S2 and S3 transmission slot sections.
According to the above-described polling of the master device, the frequency of the polling to each of the slave devices by the master device is balanced so that the transmission rate can be assigned to all of the slave devices uniformly.
However, considering the fact that the volume of transmitted data varies depending on the type of service being provided, the transmission efficiency cannot be guaranteed by the current Bluetooth communication, since all the slave devices are assigned with the uniform transmission rate regardless of service type. In other words, the assigned transmission rate is less than or greater than the service requires for data transmission.